Our objectives are to clarify the effects of maturation on the amplitude and latency of auditory evoked potentials detected under three conditions of stimulation (regular, random and self) and to determine the relative contributions of chronological age and mental age on the self-stimulation effect for auditory brain responses. We will obtain an auditory evoked response for self-delivered, machine-delivered and periodically presented click stimuli from 5 boys and 5 girls of average intelligence at ages 3, 5, 7, 9, 11, 13, 15, and 17 and from an equivalent number of bright and dull children at ages 9 and 17. Evoked response amplitude and latency data under the three conditions of stimulation will be analyzed for the identification of significant sex, age and intelligence effects.